1. Field of the Invention
The invention relates to photo-/electro-mechanical generation of hard-copy images from a CRT, light emitting diodes, a liquid crystal display, or other means, onto paper; such images being removable by the invention.
2. Discussion of Prior Art
To reduce the cost of paper for documents and the waste and expense of present recycling limitations, and for space which is limited for stocking paper, a process is needed to allow users to reclaim paper on the spot. Conventional inks for printing, typing and copying are not readily removed. An alternative process utilizing an appropriate ink is needed. The invention addresses this need with a wet printing process having the added advantage of a reusable medium requiring no master or hard copy to achieve an image on paper.
In the decorating of textiles, ceramics, metal and other surfaces, the process of sublimation-transfer is often used. Wrong-reading images are litho-, screen-, or electrostatically-printed on appropriate paper and transferred to the final product by direct contact of the printed paper with the substrate under pressure and heat. The sublimation dyes in the ink vaporize and transfer to the substrate. The extent of sublimation-how much of the dye is removed from the paper vs. how much remains-depends on the absorbancy and nature of the substrate and the time, temperature and pressure used in the transfer process. The invention uses this process, not for decorating a substrate but for removing printed images from paper.
In the decorating application of sublimation-transfer, it is not necessary to sublimate all of the ink which is printed on the paper, but, given certain conditions, it is possible to do virtually that. One condition is that the ink used be as close as possible to the raw sublimation material.
While it is possible to apply sublimating powders to paper using xerography or electrostatic processes, this requires contaminants which allow the images to develop and fix. These methods are therefore inappropriate for generating removable images.
The invention also addresses image processing and duplicating. Existing printers and duplicating devices utilize elaborate optics and complicated, often digital circuitry. These factors and the expensive toners used result in high costs. The invention requires only traditional, analog television circuitry and less expensive ink.
The use of a cathode ray tube (CRT) to transfer images to a printing medium is known in the art and is addressed in a number of patents. In U.S. Pat. No. 4,134,668 Richard Coburn shows means to optically transfer images from a CRT to a xerographic medium. In U.S. Pat. No. 3,681,527 Shizuo Nishiyama and Makoto Tanaka show a CRT "pin" tube in a similar use. In U.S. Pat. No. 4,264,912 William Okamura, Anthony Norman, and Manindra Mitra show a CRT pin tube used to form images on an electrostatic belt. In U.S. Pat. No. 4,231,061 Samuel Freeman shows a CRT with fiber-optic faceplate to expose a diazo film and describes the proper phosphors to achieve this. These methods address the use of a CRT to produce latent images on paper or media but do not show exposure of a screen printing medium as is essential to this invention and which is discussed below.